The publications and other materials used herein to illuminate the background of the invention, and in particular, cases to provide additional details with respect to the practice, are incorporated by reference.
The only commercially available fluoroalkylsiloxane is poly(trifluoropropylmethylsiloxane). It is prepared via anionic or cationic ring opening polymerization of cyclotri(trifluoropropylmethylsiloxane). Crystalline fluoroalkylmethylpolysiloxane has been obtained from the monomer of pure cis-isomer. .sup.1,2 Precursor of cyclotri(trifluoropropylmethylsiloxane) is trifluoropropylmethyldichlorosilane, prepared usually by platinum (H.sub.2 PtCl.sub.6) catalyzed hydrosilation reaction between methyldichlorosilane and 3,3,3-trifluoropropene. .sub.3 The reaction has also been applied to the preparation of bis(trifluoropropyl)dichlorosilane using dichlorosilane instead of methyldichlorosilane. Unlike non-fluorinated alkenes (ethene, propene) which give good yields between 60 and 79%.sub.4, 3,3,3-trifluoropropene gives only low yields, 26 . . . 36% in preparation of disubstituted silicon. .sub.5 Bis (1H, 1H, 2H-perfluorohexyl)dichlorosiloxane has been obtained in 42% overall yield via a two step process, where both Co.sub.2 (CO).sub.8 and platinium cyclovinylmethylsiloxane complex were used for the hydrosilylation reaction between dichlorosilane and 1H, 1H, 2H-perfluorohexane. .sub.6 High yields have been obtained via UV-light catalyzed radical reaction, .sup.7,8,9
3-(Pentafluorophenyl)ethylmethyldichlorosilane has been prepared in 70% yield from methyldichlorosilane and pentafluorostyrene. .sup.10 Cyclics having both dimethylsiloxy and 3-(pentafluorphenyl)ethylmethylsiloxane units were prepared by Matsui et al .sup.11 via hydrosilation reaction between pentafluorostyrene and cyclics containing dimethylsiloxy and methylsiloxy units. Polymerization of these cyclic was catalyzed by tetramethylammonium hydroxide, polymer M.sub.w /M.sub.n =38,000/21,000 g/mol. See Scheme 1.
Matsui also prepared hetero cyclics of dimethyldichlorosilane and 3,3,3-trifluoropropylmethyldichlorosilane or 1H, 1H,2H,2H-perfluorodecylmethyldichlorosilane via co-hydrolysis in ether. Polymerization was carried out as in the previous case.
The European patent publication EP 0563902 by Dow Corning .sup.12 describes a method for preparation of block co-copolymers from D.sub.3 and D.sub.3 -type cyclic monomers having 1H,1H,2H,2H-perfluoroalkylmethylsiloxane groups and/or vinylmethylsiloxane groups. See Scheme 2.
U.S. Pat. No. 4,814,418.sup.13 describes a similar procedure, but instead of sequential addition of monomers, they add them simultaneously, resulting a non-block copolymer. The patent covers the use of cyclic trimers of {[F(CF.sub.2).sub.a C.sub.2 H.sub.4 ](CH.sub.3)SiO}.sub.3 and {[H(CF.sub.2).sub.a C.sub.2 H.sub.4 ](CH.sub.3)SiO}.sub.3 (a=1 . . . 16) with or without D.sub.x (x=3 . . . 6) and/or D.sub.x.sup.Mevi (x=3 . . . 6, Vi=alkenyl group). The patent also claims higher molecular weight polymers by use of a phase transfer catalyst/initiator combination instead of initiator alone. Phase transfer catalyst is a quaternary ammonium or phosphonium salt and can be presented by the formulas R.sub.4 N.sup.+ X.sup.- or R.sub.4 P.sup.+ X.sup.-, where R is alkyl, cycloalkyl or phenyl group and X.sup.- is Cl.sup.- or Br.sup.-. ##STR1##